12
To exit the Tachometer Mode:
1. Press the ALT FUNCTION button and then the TACH button.
2. The TACH icon will go away.
4.5 External Delay Modes (Phase Shifting)
There are three External Delay Modes: Phase Delay, Time Delay, and
Auto (Virtual RPM). In the External Phase Delay Mode the flash is
triggered 0.1 to 359.9 degrees after each external signal pulse. The knob
sets the amount of delay in degrees. In the External Time Delay Mode
the flash is triggered 0.01 to 1000 milliseconds after each external signal
pulse. The knob sets the amount of delay in milliseconds. In the Auto
(Virtual RPM) Mode the flash is triggered by increasing amounts after
the external trigger pulse so that the image will appear to rotate at a given
(virtual) RPM or RPS. The knob sets this virtual RPM or RPS.
To enter one of the External Delay Modes:
1. Ensure there is an external input plugged in (so the unit is in
External Mode).
2. Press the Phase Delay button to cycle to the desired mode.
3. Use knob to adjust delay/angle (phase, time or virtual RPM).
To exit the External Delay Mode:
1. Press the PHASE DELAY button to cycle back to External only.
2. The word PHASE or the TIME or AUTO icon will go away.
4.6 Lock Modes – Accelerometer Input Required
In the LOCK Modes the vibration transducer (accelerometer) controls the
flash rate. Prior to setting the LOCK Mode, the strobe MUST be operated
in the Internal Mode. The accelerometer must be properly connected and
17
5.2 Balancing and Phase Measurement
The Nova-Strobe vbx contains an internally tuned filter that is incorporated
in a phase shifting network, which allows the shaft reference mark to be
directed at any convenient location on the machine while balancing or
performing motion studies (phase measurement) along a machine’s casing
or along a machine train. Examples of a convenient location are the machine’s
horizontal split line, top or bottom dead center, or the plane of the reference
transducer.
NOTE: It is advisable to “LOG” this reference location, so that it may
be utilized in future studies or balancing procedures.
To set-up for balancing or phase measurement, a data collector or vibration
analyzer must be used that is capable of interfacing with the Nova-Strobe
vbx. The instrument must then be set up to obtain and record the phase
information supplied to it from the strobe and the reference transducer.
As a general set-up guideline for the data collector or analyzer, in order to
be triggered properly and to read phase properly, check the following:
1. Set the instrument to accept an external tachometer trigger signal.
The strobe light will provide this signal.
2. Set the frequency range for order analysis (10 orders full scale works
best). This insures the 1X frequency will be centered in the 1X (first
order) filter which is a must for repeatable phase measurements.
3. Set the vibration instrument to display averaged spectrum and phase
data (4 or 8 averages).
4. Set transducer power to On.
NOTE: Application Notes are available for some data collectors that
describe their particular set-up configurations. Check the
Owners Manual for your data collector for proper setup
configurations.
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